We report that the vacuum annealing of MgO films at 225°C results in the removal of water based contamination and
the secondary electron emission coefficient increases from 0.09 to 0.15. The effective secondary electron emission yield
increases from 0.2 to 0.75 at 200 mbar chamber pressure, as temperature increases to 250 °C. The effective secondary
electron emission yield at 200, 350 and 800 mbar pressure shows similar trend during the heating as well as cooling of
the MgO sample. Thermionic emission, smaller surface band bending and the removal of impurities at high temperature
are possible reasons for the increase in secondary electrons of MgO thin films.